Simultaneous enhancement of separation selectivity and solvent strength in reversed-phase liquid chromatography using micelles in hydro-organic solvents

Abstract

The role of micelles and organic solvents as the modifiers of the aqueous mobile phase in reversed-phase liquid chromatography (RPLC) in controlling retention and selectivity is discussed. Elution strength increases in RPLC with an increase in organic solvent or micelle concentration. Simultaneous enhancement of separation selectivity with elution strength in the hybrid eluents of water-organic solvent-micelles was observed. This selectivity enhancement occurs systematically, i.e. peak separation increases monotonically with volume fraction of organic solvent added to micellar eluent, and is observed for a large number of ionic and nonionic compounds with different functional groups and for two surfactants (anionic and cationic). For two test mixtures, 13 amino acids/peptides and 15 phenols, it is shown that a better separation and shorter analysis time are observed at stronger hybrid eluents. This selectivity enhancement can be attributed to the competing partitioning equilibria in micellar LC systems and/or to the unique characteristics of micelles to compartmentalize solutes and organic solvents.

Optimization of the separation of coumarins in mixed micellar liquid chromatography using Derringer's desirability function

“…This result can be correlated to the predominantly hydrophobic properties of these solutes with respect to the other solutes. In agreement with previous reports [9,36], the results emphasize that hydrophobicities of the solute and organic modifier are important factors in controlling their interactions with the micelles which affect the solute retention in MLC. The retention time value for the analytes is also largely affected by the main factors [SDS] and C m .…”

“…The weak solvent strength of purely micellar eluents in the reversed-phase liquid chromatography can be increased by the addition of an organic modifier [2,3], which can also improve the efficiency of the chromatographic peaks [4]. Micellar mobile phase shows several advantages compared to the conventional hydro-organic eluents such as low cost, low toxicity, the possibility of simultaneous separation of ionic and nonionic compounds without needing a gradient elution, direct injection of biological fluids due to the solubility of proteins in the micelles, low volatility, detection sensitivity enhancement, unique separation selectivity [5][6][7][8], application in quantitative structureactivity relationship studies [9].…”

Micellar Liquid Chromatography from Green Analysis Perspective

“…Slow stationary phase mass transfer can be attributed to the poor "wetting" of the stationary phase with a purely aqueous mobile phase as well as to the adsorption of monomer surfactants that change the characteristics of the alkyl-bonded stationary phases [15]. To enhance the efficiency in MLC three main approaches have been adopted: addition of small concentrations of organic modifiers to the micellar mobile phase, increasing the column temperature, and decreasing the flow rate.…”

“…These modifiers increase the elution strength and often improve the shape of the chromatographic peaks. The modifiers act by solvation of the bonded stationary phase and decreasing the amount of surfactant adsorbed, such effect increases as the concentration and the hydrophobicity of the alcohol increases [15,16]. Meanwhile, the addition of triethylamine to a micellar mobile phase in combination with organic modifier enhances the efficiency over organic modifier added alone.…”

Chromatographic Separation of Heavy Metal Cations on a Silica Gel‐G with Amino Acid

“…TLC has been successfully utilized for various purposes, such as the separation of metal ions from a water sample [1], the characterization of the mobility of metal [2], and the estimation of concentration of toxic metal in industrial waste [3].The use of aqueous solution as a mobile phase in TLC was pioneered by Armstrong and Terrill [4]. Using a surfactant as the mobile phase gained popularity and became more widely applied due to its operational simplicity, cost effectiveness, relative non-toxicity and enhanced separation efficiency [5][6][7][8]. The use of silica gel and an alumina layer with surfactant mediated mobile phase systems [9][10][11][12][13][14][15] has been used to separate various inorganic species.…”